Experiments are planned with the yeast Schizosaccharomyces pombe on problems of genetic recombination and on the genetics of the sexual cycle of this yeast. Specifically, two marker effects are studied: One is exhibited by the ade6 mutant M26 with regard to gene conversion and intragenic recombination, the other is related to the frequency of mitotic crossing over in the mating-type region. The planned work includes the search for recombination-less mutants. The work on the mating-type genes, aside from being related to mitotic crossing over, also includes the study of various mutants affecting copulation and meiosis, as well as the study of S. pombe strains of different geographical origins. The overall goal is to explore the genetic regulation of the sexual cycle of S. pombe; this cycle can serve as a model system for developmental processes in eukaryotes.